Field of the Invention
The present invention relates to a hot water supply device which heats water running in a heat exchanger by a burner to supply hot water.
Description of the Related Art
Hitherto, there has been known a hot water supply device which is provided with a heat exchanger connected to a water supply pipe and a hot water supply pipe and a burner that heats the heat exchanger, and which is adapted to heat water running in the heat exchanger (refer to, for example, Japanese Patent Application Laid-Open No. 2008-138952).
Water is supplied from waterworks through a hot water supply pipe to a heat exchanger installed in the hot water supply device. The water supplied from waterworks frequently contains dissolved impurities, such as calcium carbonate and calcium hydroxide. The impurities that crystalize in a water path (heat transfer pipe) in the heat exchanger and turn into lime scale adhering to the heat transfer pipe interfere with the heat transfer in the heat exchanger, resulting in deteriorated performance of the hot water supply device.
In the hot water supply device described in the foregoing gazette, therefore, a failure of the heat exchanger caused by the adhesion of lime scale is detected by making use of the fact that, as the lime scale builds up in the heat transfer pipe of the heat exchanger, the temperature of the water in the heat exchanger increases due to residual heat (post-boiling temperature) when the supply of hot water is stopped.
When a failure of the heat exchanger caused by the adhesion of lime scale is detected, a cleaning pipe for removing the scale is connected to the water circulating path of the hot water supply device including the heat exchanger thereby to form a circulation circuit. Then, a cleaning liquid is circulated in the circulation circuit by a pump to remove the lime scale adhering to the heat transfer pipe of the heat exchanger.
However, incomplete removal of the lime scale by the cleaning leads to the detection of a failure of the heat exchanger caused by the adhesion of scale within a short period of time after the cleaning pipe is disconnected and the use of the hot water supply device is resumed, thus inconveniently resulting in the need for removing the scale again.